dbus_utility: iwyu

Manually added some missing headers. The "dbus_singleton.hpp" one is
causing issues for unit tests: unit test needs to include dbus_singleton
even if it just uses a helper function like "getNthStringFromPath".

Tested: code compiles.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I28544835a3e4483eb52f53f7ad89d233cadd4143
diff --git a/include/dbus_utility.hpp b/include/dbus_utility.hpp
index d311216..d9d59f7 100644
--- a/include/dbus_utility.hpp
+++ b/include/dbus_utility.hpp
@@ -15,11 +15,17 @@
  */
 #pragma once
 
+#include "dbus_singleton.hpp"
+
 #include <sdbusplus/message.hpp>
 
+#include <array>
 #include <filesystem>
 #include <regex>
+#include <string>
+#include <tuple>
 #include <variant>
+#include <vector>
 
 namespace dbus
 {